Gravitational Waves (GWs) were directly measured for the first time during the first observation run (O1) of LIGO in 2015, i.e., GW150914. Its source turned out to be a merging binary black holes of 36 and 29 solar masses at the distance of about 1.3 billion light years. One more observation (GW151226) during O1 (12/09/2015-12/01/2016) and four observations (GW170104, GW170608, GW170814 & GW170817) during O2 (30/11/2016-25/08/2017) have been announced. Virgo started its operation on August 1, 2017 and measured GW170814 and GW170817 jointly together with two LIGO observatories, resulting in the sky localization of the source about 10 time better than what would have been obtained by two LIGOs only. The first four observations were all from stellar-mass binary black holes, and are giving many interesting implications on black hole formation and its evolution. The most recent GW observed was from a merging binary neutron star, and EM signals such as gamma-ray, light, X-ray and radio were observed as well. We are indeed in the era of GW Astronomy already, and the 2017 Nobel Prize in Physics has been awarded to Rainer Weiss, Kip Thorne and Barry Barish for their pioneering contributions to the LIGO detector and observation of gravitational waves. In this talk, roles of three laureates and some of the main science results obtained in GW observations so far have been summarized. Current activities in GW detection experiments and its perspectives are also discussed briefly, including the SOGRO project in Korea.